2009-09-05

Spirit Sol 240

Our email problems and the attendant scheduling problems continue, but it seems to be getting better. I arrive an hour early -- thinking I'd be only half an hour early, but the schedule started later than I thought. No problem. Early is no problem.

The day is ambitious. In the morning we MB-touch the soil and start a short APXS integration. After that, the fun begins: we'll do a 2x2 mosaic of MI stacks around the chosen target, hold the RAT out where the PANCAM can image its magnets, then MI the capture and filter magnets (which are located on the rover body, at the base of the mast). Last, we'll place the MB on the filter magnet.

As on previous sols, we're planning in the blind here; the downlink doesn't start until the SOWG meeting is nearly over. When we get the images, I'm at first satisfied -- then concerned. (Then ... kind of sleepy ... no, wait. Leave it at concerned.) Something looks wrong with the final front HAZCAM, and after a minute I realize what's bothering me. It's too level.

We wanted to end this drive with a better insolation (solar tilt). Stopped on the slope, with the solar panels aimed at the sun, would be good. Level is bad. It's hard to tell, but the picture looks level.

Oh, shit.

This means we're going to have to scrap the planned IDD work for the sol and hope we can work out a backward drive upslope -- and hope like hell that that drive works.

But before I panic, I check the image headers and do a little math. Our roll is -11.6 degrees, pitch -7.0 degrees, making our overall tilt about 13.5 degrees. RSVP's predictions varied depending on which terrain mesh you used, but it tended to show more like 20 degrees. So this looks bad.

What the hell happened? I ignore the remainder of the meeting, load yestersol's sequence into RSVP and simulate it. Like yestersol, I look at 10% slip (15cm) and 20% slip (30cm). Then I do something I should have done yestersol: I consider worse slips. At 33% slip (45cm) the predicted HAZCAM in RSVP comes out looking almost identical to the actual we just received.

So now we know what went wrong. It was exactly what I was worrying about during the CAM: we slipped more than expected, to the point where we started to level out.

I think hard for a minute about how I want to handle this. As the SOWG meeting breaks up, I activate my mike and tell Ray we might have a problem.

"We don't know that we have one," I tell him, "we'll have to do some more analysis first. But I wanted to let you know we might have to replan the sol to drive instead."

To my surprise, Ray sounds unconcerned. "Okay," he says calmly, "you guys figure it out and we'll do what we need to do."

First I go talk to Rich Petras, the Mobility/IDD guy on duty today. He agrees with me about the slip results (foo!) but doesn't know how to compute the insolation factor from tilt. Neither does our ACS guy, though he's able to show me what the rover will look like as seen from the sun. It looks good, good enough to start me thinking that we might be able to stay put after all. Then again, I don't have a sense of how good it needed to look. On a scale of 0.0 to 1.0, we needed to be about 0.88. Yestersol, we were at about 0.91; if we worsened at all, the rover will survive but we'll feel like dumbasses (that is, I'll feel like a dumbass). We were hoping for something like 0.94 or 0.95. And I can't visually distinguish an attitude that would lead to 0.88 insolation from one that would lead to 0.95 insolation. We need math.

Chris is thisol's floater, and he's in the sequencing MSA when I

return."I think we might not need to drive, so I want to get started on the IDD stuff," I tell him. "Can you figure out what our insolation is?"

"Already working on it," he says. He's slinging Perl to get us an approximation.

So he works on that, and I work on the IDD stuff. The script, when he finishes it, reports about a 0.89 or 0.90 insolation, which would be a dropoff from yestersol but good enough that we don't have to move. But only a minute or so after he finishes, Leo Bister comes in with the official word: we're over 0.93. Not only are we good enough, we improved. Not as much of an improvement as we'd hoped, but an improvement all the same.

There's also good news about my IDD sequencing. It's all going smoothly, almost suspiciously smoothly. The scientists have picked a their soil target -- Uxmal, a nice spot right in front of us. When I plug Uxmal into the sequence and run a simulation in RSVP, it works the first time. This is uncommon enough that I go back and check it, but, yes, it really is going to work.

I'm more or less done with the sequence and starting to do the detail work, when Bethany comes in with a request. They've just taken a close look at the PANCAM and there's a perfect patch of soil just by the right front wheel, which is a region that's generally awkward to IDD in. (As it happens, this spot would have been smack in front of us -- in ideal IDD territory -- if we hadn't slipped.)

"Can you get to it?" she asks.

Well, what the hell, I'm game. Everything else seems to be going my way today. She reads off the new target's coordinates and surface normal; I tell RSVP about it, tell the sequence to go there instead of to Uxmal, and simulate it. I'm all prepared for RSVP to spew errors that will take me hours of work to clean up, but nothing doing: like Uxmal, the new target works perfectly the first time.

I'm on a roll, baby.

I have a lot of little details left to attend to, and I even find time for polishing the sequences some. I love it when I find a way to shave a few seconds out of the sequence, to make it just that little bit more elegant -- not only for its own sake, but also because every second we save, every Watt-minute we can squeeze out of the engineering side, we can spend on science. And that's what we're here for, after all.

One of the reasons I have all this time is that, well, let's face it, I'm awesome. But another reason is that there are problems elsewhere in the plan that, like yestersol, slow us down significantly. Once again, we run hours late. Kevin says, "I thought yestersol was the suckiest sol ever. I was wrong. This sol is the suckiest sol ever."

I'm okay with it. My stuff's long since done and I'm ready for conjunction, but more importantly -- much more importantly -- I got a chance to do something I'd been hoping for since the beginning of the mission.

Most of the targets and features we encounter are named by the science team. Every once in a while, the rover drivers get to name something -- I've gotten to do it once or twice -- but it's not common. It's very cool to name something on another planet. The names aren't official, but they do tend to stick; and as when we RAT something, there's a sense of permanence to it.

Since the beginning of the mission, I've been hoping to name something in honor of Jake, since he died only a couple of months before we landed. It didn't seem like the right time when I had the other chances. This one felt right. I don't know why; maybe it's because I've been thinking about him lately, since we moved. Maybe it's some other reason.

Anyway, it fell to me to name the target we abandoned Uxmal for. The tiny little patch of soil our rover will be protecting from the wind throughout the long night of conjunction has a name: "GreenEyes." I miss you, buddy.[1]